An organic light emitting device is composed of two opposing electrodes and organic material thin films including a plurality of layers having a semiconductor-like property interposed therebetween. The organic light emitting device having the configuration uses a phenomenon in which electric energy is converted into light energy by using an organic material, that is, an organic light emitting phenomenon. Particularly, when a voltage is applied between two electrodes in a structure in which an organic material layer is disposed between an anode and a cathode, holes from the anode and electrons from the cathode are injected into the organic material layer. When the injected holes and electrons meet each other, an exciton is formed, and the exciton falls down to a bottom state to emit light.
In the aforementioned organic light emitting device, light generated from the organic material layer is emitted through a light transmissive electrode, and the organic light emitting device may be typically classified into a top emission type, a bottom emission type and a dual emission type. For the top emission or bottom emission type, one of two electrodes needs to be a light transmissive electrode, and for the dual emission type, both of the two electrodes need to be light transmissive electrodes.
In respect to the aforementioned organic light emitting device, many studies have been concentrated since Kodak Co., Ltd., announced that when a multilayer structure is used, the device may be driven at a low voltage, and recently, a natural color display using the organic light emitting device is attached to a mobile phone and commercialized.
Further, as recent studies on the organic light emitting device using a phosphorescent material instead of an existing fluorescent material have been conducted, efficiency has been rapidly improved, and it is also expected that the device may be replaced with the existing lighting in the near future.
In order to use the organic light emitting device as lighting, the device needs to be driven at high brightness unlike the existing natural color display, and to maintain a constant brightness similar to the existing lighting. In order to sufficiently improve the brightness of the organic light emitting device, light needs to be emitted in a large area, and in order to implement light emission in the large area, a high driving current needs to be used. In addition, in order to maintain the constant brightness in the large area, the aforementioned high current needs to be uniformly injected into the device having a large area.